Exhausted

And a tired old pun to boot.

Yesterday, I learned that our kitchen fan (which has of late been making horrible grinding motor-burning-out kind of noises) is only a kitchen fan by location, not by design.  It was actually a bathroom model, designed to vent air laden with moisture, but not much else.  Quoth the electrician (lightly paraphrased), "So how long has this been in here?  Four, five years?"  "Oh, no," says I.  "At least 13."  "Heavens to Murgatroyd!" he exclaimed.  "I would have expected it to expire years gone by, from all of the aerosolized grease that it has had to move!"

Of course, we had to replace it with another similar model (since the alternative would have required a great deal more money, time, and the ripping up and excavating of the kitchen ceiling), but at least now we know that if it lasts at least 5 years we'll have gotten our money's worth.

Weekend Roundup

This long weekend past afforded several opportunities to learn and try new things.  Here are two of them.  Tra la.

First, we broke and had to clean up our third (3rd) compact fluorescent light bulb, commonly abbreviated to "that goddam thing."  Three mercury spills is at least two too many, and we've had enough-- we're jumping ship.  One of the two table lamps received one of our precious stock of incandescents (cunningly stored in plain sight, a la The Purloined Letter, in a different lamp that doesn't get used much), and the other?  Ah, the other.  The other received a shiny new LED light bulb, rated at something like 800 lumens.  It cost 12 bucks, and I'm a little nervous, as reviews of other such bulbs suggest that their reliability... well, isn't.  But even if we end up having to replace it in 6 months (rather than the 20 years some have claimed), I think the piece of mind of not having to clean up mercury is probably worth it.

Secondly, on Sunday we took the dog and joined a (semi)local dog walking group for a roughly 4-5 mile hike.  Ok, not so much "hike" as "meander", but it was still nice-- especially for a couple of learning experiences.  We were on an isolated farm trail, away from roads and traffic, so we (somewhat nervously) let our slightly less than a year-old puppy Jet off of his leash for the first time in public.  Whereupon we learned the first thing-- he may not, in fact, have been named Jet because of his ebon hue.  He was likely named Jet because that's how goddam fast he was.  Holy CRAP fast.  30 mph?  Possibly more at full tilt?  (Greyhounds can go over 40, but I'm not sure he was quite that fast).  I'm pretty sure it'd take an Olympic sprinter to have a hope of keeping up with him in the full stretch.  This, amid our astonishment, also gave us a touch of concern, obviously, whereupon we learned the second thing-- when we called, he came right back.  Immediately.  This was astonishingly reassuring, and he spent most of the next hour or so off leash, running back and forth around the group, making friends and getting valuable experience interacting with other dogs.  Much love to Martha, the 9 year old lab who was willing to smack him around verbally and physically until he behaved.  (Side note-- we're beginning to suspect, based on some of his reactions, that his dam was a lab, and his father the shepherd).  He learned a lot about good behavior, and we learned that we could trust him off leash, at least in some circumstances.

Das Blinkenlights

The principle of LEDs is basically the same as that of any other diode-- current, in the form of electrons, flows from one side to the other, but not back.  OK, technically the electrons go the other way around, because they're negative, and it's really confusing but its codified in convention and there's nothing we can do about it*.  Anyway, the particular materials used in LEDs can also be charged by current with a large number of "holes."  These are not physical holes, but rather a sort of "anti-" electron**.  They're empty spaces in atoms that normally would hold electrons, but for whatever reason don't.  When the electrons meet the holes, they "fall in."  This "fall" is a lot like a physical fall, in that it releases some potential energy, in the form of a photon***.  The amount of energy released determines the energy of the photon, and therefore the wavelength, and therefore the color.  Some colors (red) are a lot easier to generate, whereas some (blue) require some fairly complicated chemicals and materials to create.  White LEDs often rely on a two-stage approach, generating blue and ultraviolet photons that also activate a phosphor coating that in turn generates yellow photons, which mix with the blue to get something whitish.


*Damn you Benjamin Franklin!


**The actual antielectron is a positron, which is completely different, being a particle with the same properties as an electron except for opposite charge.  Holes are just absences of electrons.


***I accidentally typed "phorm of a photon" here, but decided to remove it.  You're welcome.

All up and down my left side

Electronics have always been a bit of a weak spot with me.

When I was a wee blogger, I had a "Science Fair 150 in 1 Electronic Project Kit (Cat No. 28-248)."  Ok, technically I still have it, rescued from my parent's basement a few years ago.  Basically, it consists of a board with a number of installed circuit elements-- capacitors, resistors, etc., plus some outputs (a light bulb, a rudimentary LED number display, a speaker, etc).  There's an included booklet that tells you how to hook various things up to other various things in order to get various results-- flashing lights, musical tones, timers, and so on.  I eagerly followed the instructions, and got the effects, but had no real idea of what was going on-- I just followed the directions like a recipe.

So now, today, [mumblety] years later, I'm setting out to rectify the situation.  (Get it?  Rectify?  That's an electrical engineering joke!)  So here, more or less, is how a diode works.

A diode, according to the dictionary, is "an electronic device that has two electrodes or terminals and is used especially as a rectifier."  Not very helpful, actually.  Electrodes/terminals I know, those are the "ends" of a circuit element, that can be attached to other elements.  A rectifier (see, I told you it was an EE joke), as it turns out, is "a device for converting alternating current into direct current."  Ok, that makes more sense to me.  So a diode is an electronic device that has two ends and is usually used to turn AC into DC (generally not the other way around).  But how?


A diode is, somewhat simplified, a chunk made up of two types of material with a wire sticking out of each bit.  The two sections have specific electrical properties such that the boundary between them allows current to flow only in one direction (at least theoretically). The details on how that works rapidly get very technical, so I'll leave it there, at least for now.  The point is that alternating current builds up on one side of the diode, like waves crashing upon a semiconductor levee (this is getting unexpectedly poetic), and when the waves get large enough, the "water" begins to flow down the other side, away from the barrier.


This has some useful effects, besides the simple rectification property.  The threshold at which the diode allows current to start flowing (the "height of the levee," as it were) is dependent on temperature, so a diode can be used as a simple temperature sensor-- if current is flowing, it must be at least X degrees (where X depends on the type of diode).  They can also temper current surges, like tiny little surge protectors.  And finally, there's the ubiquitous LED, or Light Emitting Diode, poised to be not just Das Blinkenlight on your device, but also a replacement for your household bulbs.  This is starting to get awfully long, so I think I'll stop here, and cover LEDs more specifically tomorrow.